Add landing page, redesign emails, and return updated task on completion

- Integrate landing page into Go app (served at root /)
- Add STATIC_DIR config for static file serving
- Redesign all email templates with modern dark theme styling
- Add app icon to email headers
- Return updated task with kanban_column in completion response
- Update task DTO to include kanban column for client-side state updates

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/dto/responses/task.go

@@ -73,6 +73,7 @@ type TaskCompletionResponse struct {
 	Rating      *int                          `json:"rating"`
 	Images      []TaskCompletionImageResponse `json:"images"`
 	CreatedAt   time.Time                     `json:"created_at"`
+	Task        *TaskResponse                 `json:"task,omitempty"` // Updated task after completion
 }
 
 // TaskResponse represents a task in the API response
@@ -99,10 +100,11 @@ type TaskResponse struct {
 	ContractorID    *uint                    `json:"contractor_id"`
 	IsCancelled     bool                     `json:"is_cancelled"`
 	IsArchived      bool                     `json:"is_archived"`
-	ParentTaskID    *uint     `json:"parent_task_id"`
-	CompletionCount int       `json:"completion_count"`
-	CreatedAt       time.Time `json:"created_at"`
-	UpdatedAt       time.Time                `json:"updated_at"`
+	ParentTaskID    *uint        `json:"parent_task_id"`
+	CompletionCount int          `json:"completion_count"`
+	KanbanColumn    string       `json:"kanban_column,omitempty"` // Which kanban column this task belongs to
+	CreatedAt       time.Time    `json:"created_at"`
+	UpdatedAt       time.Time    `json:"updated_at"`
 }
 
 // Note: Pagination removed - list endpoints now return arrays directly
@@ -340,3 +342,55 @@ func NewTaskCompletionListResponse(completions []models.TaskCompletion) []TaskCo
 	}
 	return results
 }
+
+// NewTaskCompletionWithTaskResponse creates a TaskCompletionResponse with the updated task included
+func NewTaskCompletionWithTaskResponse(c *models.TaskCompletion, task *models.Task, daysThreshold int) TaskCompletionResponse {
+	resp := NewTaskCompletionResponse(c)
+
+	if task != nil {
+		taskResp := NewTaskResponse(task)
+		taskResp.KanbanColumn = DetermineKanbanColumn(task, daysThreshold)
+		resp.Task = &taskResp
+	}
+
+	return resp
+}
+
+// DetermineKanbanColumn determines which kanban column a task belongs to
+// Uses the same logic as task_repo.go GetKanbanData
+func DetermineKanbanColumn(task *models.Task, daysThreshold int) string {
+	if daysThreshold <= 0 {
+		daysThreshold = 30 // Default
+	}
+
+	now := time.Now().UTC()
+	threshold := now.AddDate(0, 0, daysThreshold)
+
+	// Priority order (same as GetKanbanData):
+	// 1. Cancelled
+	if task.IsCancelled {
+		return "cancelled_tasks"
+	}
+
+	// 2. Completed (has completions)
+	if len(task.Completions) > 0 {
+		return "completed_tasks"
+	}
+
+	// 3. In Progress
+	if task.Status != nil && task.Status.Name == "In Progress" {
+		return "in_progress_tasks"
+	}
+
+	// 4. Due date based
+	if task.DueDate != nil {
+		if task.DueDate.Before(now) {
+			return "overdue_tasks"
+		} else if task.DueDate.Before(threshold) {
+			return "due_soon_tasks"
+		}
+	}
+
+	// Default: upcoming
+	return "upcoming_tasks"
+}